Heat exchanger with variable configuration



Dec. 15, 1964 J. E. AHERN HEAT EXCHANGER WITH VARIABLE CONFIGURATION 4Sheets-Sheet 1 Filed March 20, 1961 INVENTOR. JOHN E. AHERN BMW ATTORNEYDec. 15, 1964 J. E. AHERN HEAT EXCHANGER WITH VARIABLE CONFIGURATION 4Sheets-Sheet 2 Filed March 20, 1961 n QE INVENTO N E. AH N ATTORNEY w OEDec. 15, 1964 J. E. AHERN 3,161,233

HEAT EXCHANGER WITH VARIABLE CONFIGURATION Filed March 20, 1961 4Sheets-Sheet 3 "Hummnmnm FIG. 3

INVENTOR. JOHN E. AHERN ATTORNEY Dec. 15, 1964 J. E. AHERN 3,161,233

HEAT EXCHANGER WITH VARIABLE CONFIGURATION Filed March 20, 1961 4Sheets-Sheet 4 INV EN TOR.

6 L8 47 JOHN E. AHERN ATTORNEY United States Patent Ofitice 3,161,233Patented Dec. 15, 1964 efficient.

3,161,233 IEAT EXCHANGER WETH VARIABLE tCGNFIGURATIGN John E. Ahern,Granada Hiils, Caiif., assigner to The Marquardt Corporation, Van Nuys,Calif., a corporation of California Filed Mar. 20, 1961, Ser. No.97,4175 3 Claims. (Cl. 165 101) This invention relates to a heatexchanger with variable configuration, and more particularly to a heatexchanger operable over a wide range of conditions under which inlettemperature and inlet pressure of a fluid to be cooled increase by aconsiderable amount.

A heat exchanger for cooling at fluid having a relatively low inletpressure and temperature should preferably have a large face area and ashort flow depth for the fluid. However, when the inlet fluidtemperature increases, a small face area and a long flow depth is moreOf course, a long flow depth results in a considerably higher pressureloss through the heat exchanger and the higher pressure loss must bepermissible because of an increase in inlet pressure. It has beenproposed to supply an aircraft with liquid hydrogen as a source of fueland to utilize the hydrogen to continually liquefy ambient air obtainedfrom a scoop to provide an oxidant for the hydrogen. The ambient airentering such a cooling system would have a low inlet temperature andpressure at approximately sea level operation of the aircraft but athigh altitudes and high flight speeds, high inlet temperature andpressure conditions would prevail. Thus, the heat exchanger arrangementwhich would be optimum for sea level flight conditions would not be themost suitable for the high altitude flight where a much larger airpressure loss is permissible and the air must be reduced in temperatureby a substantially greater degree.

The heat exchanger of the present invention makes use of a bafflingsystem for varying the configuration of the heat exchanger so that itpresents a large face area to the air flow and a short air flow depth atsea level operation. At high altitude operation, the battles are movedinto a position wherein a small face area and a long air flow depth isprovided. Thus, for a fixed arrangement of heat exchanger tubing, theheat exchanger can operate over a wide range of conditions withincreased performance eliiciency. When the baffles for the heatexchanger are positioned to present a small face area, the length offlow through the heat exchanger will be substantially greater and alower refrigerant flow will provide the same airside performance as whenthe maximum face area configuration is used.

in the invention, the air is obtained from ascoop located exteriorly ofa fuselage, and a pair of baffles can be moved to cause the air to flowserially over three separate sections of the heat exchanger under high.altitude flight conditions. For sea level operation, the three sectionspresent one large face area of less depth since the baflies do notdivide the air flow. When higher inlet temperatures and pressure areencountered, the large side face area is closed off and air isintroduced to the end of I the heat exchanger to provide a substantiallylonger flow depth through the heat exchanger for the air. With thegreater flow depth, the velocity of air through the exchanger will besufiiciently higher because of the higher inlet pressure, and this willresult in increasing the airside heat transfer coeflicient and theperformance efliciency of the heat exchanger. Also, lower coolant flowscan be utilized because of this high airside eificiency. For maximumperformance, cross counter flow of the fluids is maintained by the useof suitable valving.

It is therefore an object of the present invention to provide a heatexchanger of variable configuration in which optimum performance isavailable under conditions of low available pressure loss and inlettemperature and at conditions of high available pressure lossaccompanied With high inlet temperature.

Another object of the present invention is to provide a heat exchangerin which the configuration can be changed by movable bafiiing to providea large face area and short flow depth or a small face area and longflow depth.

Another object of the invention is to provide a heat exchanger in whichthe air flow path through the heat exchanger can be varied in accordancewith inlet temperature and available pressure loss and in which thevalving of the heat exchanger can provide for cross counter flow of thetwo fluids regardless of the air flow path.

A further object of the invention is to provide a heat exchanger withvariable configuration which is suitable for liquefying air obtainedfrom the atmosphere during flight with a low temperature liquid fuel,such as hydrogen, and which has optimum performance over a large rangeof flight conditions.

These and other objects of the invention not specifically set forthabove will become readily apparent from accompanying description anddrawings in which:

FIGURE 1 is a perspective view of the first form of the inventionshowing the batfies for changing the heat exchanger configuration.

FIGURES la and 11) show the position of the valves for the configurationof FEGURE 1.

FIGURE 2 is a vertical section along line 2-2 of FIGURE 1 showing thethree sections of the heat exchanger and the bafiies in position toprovide a large face area and short flow depth for the air.

FIGURE 3 is a partial view of the manifold of the heat exchanger ofFIGURE 1 showing the direction of coolant flow when the baffles aremoved to provide a small face area and a long flow depth.

PEGURES 3a and 3b show the position of the valves for the configurationof FEGURE 3.

FIGURE 4 is a vertical section similar to FIGURE 2 showing the positionof the baffles for a small face area and a long flow depth.

FEGURE 5 is a section along line 55 of FIGURE 2 showing the constructionof one of the baflies.

FIGURE 6 is an enlarged sectional View, partly in elevation, of one ofthe valves for controlling the coolant flow to the various sections ofthe heat exchanger.

FIGURE 7 is a sectional view along line 7--7 of FIG- URE 6 showing thepassages of the inlet coolant valve during normal sea level operation.

. FIGURE 71: is a sectional view similar to FIGURE 7 showing thepassages of the outlet coolant valve during normal sea level operation.p

FEGURE 8 is a sectional view along line 8-8 of FIG- URE 6 showing thepaths through the inlet coolant valve during high speed, high altitudeoperation.

- tained within the fuselage.

, FIGURE 8a is a sectional view similar to FIGURE 8 showing the pathsthrough the outlet coolant valve during high speed, high altitudeoperation.

Referringto the form of the invention illustrated in FIGURE 1, a passagehas an inlet 21 for receiving the fluid to be cooled, such as ambientair. The inlet 21 can be in the form of an air scoop located exteriorlyof an aircraft fuselage and the passageportion 22 is con- Passage 20'contains an enlarged bend portion 23 across which extends heat exchanger24, and air discharged from the heat exchanger is directed by passageportion 22 to the outlet end25. In the event that the air or other fluiddischarged from heat exchanger 24 is to be liquefied, the outlet end 25will connect with additional heat exchangers (not shown) for thispurpose.

The heat exchanger 24 is comprised of three separate sections 27, 28 and29 and each of the sections has four separate passes 30, 31, 32 and 33across the enlarged passage portion- 23. Upper manifolds 34, 35 and 36connect with the end-of passes of each of the sections 27, 28

and 29, respectively, and lower manifolds 37, 38 and 39 connect with theend of the passes-33 for each of the sec-p tions 27, 28 and 29,respectively; The tubes of the multiple passes of each section are inseries 'a'ndth'e passes are connected together at-the ends of the heatexchanger by bent sections 40, such as illustrated for connecting thepasses 31 and 32 of all the sections. The inlet passage '45 whichconducts the coolant, such as liquid hydrogen, to the heat exchangerdivides into passages 46, .47 and 48 which connect, respectively, withthe upper manifolds 34, and 36 of the heat exchanger section. A valve 49connects the passage with the various branch passages '46, 47- and 48and this valve determines the direction of flow into the various branchpasses. In a similar manner, the outlet passage 50 is connected 'atvalve 51 with branch passages 52, 53 and 54 which'com'municat'e withlower manifolds 37, 38 and 39, respectively. The setting of the valve 51determines the directio'n of vflow in the various branch passages 52, 53and 54.

. 4 by a flexible link 66 in order to move the baflle along the tracks.The presence of the movable bafiles 57 and 63 make it possible to varythe configuration of the heat exchanger 24 to permit air entering thepassage 20 to pass through all the heat exchanger sectionssimultaneously to provide a large face area and a short air flow"depthor to pass through the sections one after another to provide a smallface area and a long air flow depth.

In FIGURE 2, the bafile 57 is located along the bottom of the duct andthe battle is located altirig the top sur= face of the turn portior'i 23so that neitherhafil'e inter feres with, the flow of the air through theassage 2th Thus, the air flows through the sections 27, as, and 29 ofthe heat exchanger 'simultarieousl'y, and the heat x= changer provides alarge face area and a short flow depth: In FIGURE 4, the baffle 57 hasbeen moved to extend between the bottom of thep'assage 20 and thejunction between sections 27 and 28 so that the baflle 57 extendscompletely across the passage; Also, thebafile '63 has been movedtoextend between upper surface of passage 20 and the .jllnCtlOll betweenheat exchanger sections 23 and 29.-1 Thus, all of the air enteringthepassagego is diverted by bafile" 57 through" the heat exchanger 27. andis then diverted by bafiieifi, through the section 28 and finally, allthe aiiflows through theheat exchanger sec tion 29. Therefore, the heatexchanger. 24 presents to the air a small face area, namely that of anindividual section, and a long now depth, namely the combined flow depthof all three heat exchanger sections;

It is understood thatthe position of the bane; 57 and 63 in FIGURE 2Will be utilized both the fillet temperature; and pressure arerelatively low so that suffi cient cooling can take place through the"depth of one section and the pressure drop through this on'e' deptli iscompatible with the low inlet pressure. When them .let temperature andpressure greatly increases the hatlies 57 and 63 aremoved to thepositions of '4 so that theair in serially transversing the three heatex- When the air flow is unobstructed through the turn to provide a longflow depth and a small face area. Each side of the turn portion 23 ofthe passage 20 is equipped with a channel track 56 which extends alongthe inlet portion and curves upwardly to terminate at the locationbetween the sections'27 and 28 of the heat exchanger. A flexible bafiie57 is supported betweenthe channels 56 by a plurality of rods 59 havingrollers 58at opposite ends which are guided by the channels. The bafilescan be made of'corrugated sheet material in order to conform to thechanging shape of the channels 56 and the rods 59 extendbetween spacedcorrugationstsee FIGURE. 5),

A-linear actuator, 60 of any .well known suitable construction canbeconnected by a link 61 with the bafile57in order to move the same alongthe channel tracks 56.:

A second set of channel tracks 62 are located downstream of the heatexchanger 24 on opposite side's of, the

I flight conditions.

changer sections can still be reduced to the desired outlet temperature,The passage of the air through these three sections results in asubstantially increased pressure loss but this pressure "can be acceptedbecause of the increased inlet pressure available. As previouslydiscussed,

the configurations of FIGURES *2 and 4 ar'e 'suitable for use in anenginewhi hiiquefies ambient air with a low temperature supply of fuel,such ashydrogen, 'Theconfiguration of FIGURE 2 is p artic'ulanlysuitable to sea levelv static operation while, the/configuration of FIG-URE 4 is particularly suitable to high altitude high speed In order toobtain maximum performance from both configurations of theheatexchanger, across counter flow arrangement of the'fluids for bothconfigurations is pro \fidedand this is accomplished bythe yalvestructures of valves 49 and 51." Referring to FIGURE. '6, the struc tureof-valve 49"is illustrated and it is understood that the valve v51 hasvan identical. structure; The valve 49 comprises -a-:casing "containinga'vallve plugfll. The: i

passages45, 46, 47, and 48 terminate at openings spaced 90 degreesaround the casing 70. At one cross section, illustnated; in FIGURE 7,the plug '71 ,contains'four cross passages 72', L73, 74, -;and whichconnect the passages 1. i45481with one another; at acentral terminal 76'when the duct 20. v The forward portions of these tracks commence atthe: outer side of section 27 and curve'along the upper" surface ofturnportion -23. T ea t portions of the tracks: 62 curve across theduct20 '-and terminate at a location between the heat exchangersections. 28 and 29. A

flexible baflle 63, similar in construction to baflie"5,7, is v-'movablealong the tracks 62on'rollers 64 connected to? the end ofshafts extending through the .corruga'tioni A1 linear actuator '65 canbe-locatedat theendofi one of the channel tracks 62 and is connectedwiththe bathe 63 j external ports; 3

,valve .71 is positionedfto the left. Similarly, when the alve plug 71'of valve' -51} is positioned; to the left,-cross passages '72, 73 74',and 75' connect the I passages 50', 52, 53, jand54 with one anothenatthe'centralterminal 76 Whn the valve plugs 71fand 71'-of.. valve-49and51,.

respectively, aremoved totheright in :FIGURE. 6, the section illustratedin FIGURES 8.a:nd18a,align with tha In FIGURE 8, plug 71 of valve 49con-- tains two paseages 80' and- :81 which are, separate fr'om v oneanother, and-"passage80 connects the passages 45 and'48 'while thepassage 81connects passages 46' and 4,7.

H 3 In FIGURE 8a, the plug 71 of valve 51 contains passages 80 and 81'and passage 80' connects between passages 50 and 52 while passage 81'connects between the passages 53 and 54. The plugs 71 and 71' for thevalves 49 and 51, respectively, are each connected by a shaft 83 to alinear actuator 84 which serves to move the valve plugs between thepositions shown in FIGURES 7 and 8. A bellows S5 prevents leakage fromthe casing 70 and a pressure equalizing vent 86 prevents trapped fluidfrom interfering with the movement of the plugs. Any suitable signal canbe introduced to the actuator 84 through lines 87 to move the valveplugs 71 and 71 into one of their two operating positions.

In the operation of the heat exchanger with the baflles in the positionof FIGURE 2, the plugs 71 and 71' of the valves 49 and 56 are in theposition shown in the FIG- URES 7 and 7a, respectively, to provide forcross counter flow through the sections of the heat exchanger 24. Thelow temperature coolant is introduced through passage 45 equally to allof the passages 46, 47, and 48 through the passages 72-75 in the valveplugs 71. Manifolds 34, 35, and 36 introduce the coolant to the firstpasses 30 of the heat exchanger sections 27, 28 and 29, respectively.The coolant flows serially through passes 30, 31, 32, and 33 of each ofthe heat exchanger sections and the manifolds 37, 38, and 39 receive thedischarge coolant. Passages 52, 53, and 54 direct the discharged coolantthrough passages 73, 74', and 75 of valve 51 to the outlet passage 50.

When liquid hydrogen or other fuel is utilized as the coolant, theoutlet passage 5!) can lead directly to a propulsion means for anaircraft in which the hydrogen can be combusted with an oxidant toproduce thrust. Since the coolant flows in a cross counter flowrelationship with the incoming air with the valve arrangement of FIGURES7 and 7a, an efiicient heat transfer relationship exists wherein thewarmest air encounters one side of the heat exchanger and the coldestcoolant enters the other side. Thus, at sea level flight conditions, alarge face area and a short air flow depth can be accompanied by crosscounter flow of coolant.

In the operation of the heat exchanger with the bafilles in the positionof FIGURE 4, plugs 71 and 71' of the valves 45 and 5t) are in theposition shown in FIGURES 8 and 8a, respectively, to provide for crosscounter flow through the sections of the heat exchanger. The lowtemperature coolant is introduced through passage 45 and all of thecoolant is directed through valve passage 86 and passage 48 to themanifold 36 of section 29. As the coolant flows serially through thepasses 30-33 of the section 29, it will be flowing in cross counter flowrelationship with the air entering this section and flowing in thedirection of arrow 9%) (see FIGURE 4). The coolant discharged from thesection 29 is directed by passage 54 and valve passage 81 to the passage53 entering the manifold 38 for the heat exchanger section 28. A coolantthen flows through the four passes of heat exchanger 28 and isdischarged at manifold 35, which is connected by passage 47 with passage46 through valve passage 81 of valve 49. Since all the air is flowing inthe direction of arrow 91 (see FIGURE 4) over the heat exchanger sec--tion 28 and since the coldest coolant enters the rear manifold 38, thecross counter flow relationship is maintained in the section 28. All ofthe coolant is then directed by passage 46 through the manifold 34 toheat exchanger section 27. The coolant flowing through the four passesof section 27 is discharged at the manifold 37 and then is conductedthrough passage 52 and valve passage 80' of valve 51 to the outletpassage 50. The direction of the air flow over the section 27 isillustrated by arrow 92 (see FIGURE 4) so that it is apparent that thecross counter flow of the coolant is still maintained since the coldestfluid enters the manifold 34.

. It is understood that suitable control means can be utilized tocorrelate the positions of the valve plugs 71 i and 71' of the valves 49and 51 with the positions of the baflles 57 and 63. When the baffles aremoved into the airstream, as illustrated in FIGURE 4, to provide a smallface area and a long air flow depth, the plugs 71 and 71' are moved tothe right in FIGURE 6 to provide the flow paths shown in FIGURES 8 and8a. On the other hand, when the baffles are in their stored position, asillustrated in FIGURE 2, the actuator 84 will maintain the plug 71 and71 in the position corresponding to FIGURES 7 and 7a so that crosscounter flow will be maintained with a large face area and a short flowdepth. The number of passes of each of the heat exchanger sections canbe varied in accordance with any desired operational char acteristicsand also the numbers of sections which make up the heat exchanger can bevaried in conformance with any desired characteristics. It is understoodthat because of the higher pressure drop across the configuration ofFIGURE 4, the small face area of this configuration can provide the samemass flow as the large face area of FIG- URE 2 which operates under asmaller pressure differential. Also, since the temperature entering theconfiguration of FIGURE 2 is lower than that entering the configurationof FIGURE 4, the greater amount of cooling in FIGURE 4 can provide adischarge temperature substantially the same as that leaving theconfiguration of FIGURE 2.

It is apparent that various other types of heat exchanger arrangementscan be utilized where the heat exchanger is divided into sections andbaffling is used to conduct the air in sequence to heat exchangersections when a long air depth flow path is required. Any suitablevalving for the cooling and various actuations for the shutters andbattles can be used. Various other modifications are contemplated bythose skilled in the art without departing from the spirit and scope ofthe invention as hereinafter defined by the appended claims.

What is claimed is:

l. A heat transfer device having a configuration variable with operatingconditions comprising heat exchanger means located transversely within aduct through which flows a fluid to be cooled, said heat exchanger meanscomprising a plurality of heat exchanger sections located side by saidin a plane transversely across said duct, a first movable baflle locatedwithin said duct upstream of said heat exchanger means and located alongthe surface of the duct to provide a configuration of large face areaand short flow depth, a second movable baflle located within said ductdownstream of said heat exchanger means and located along the surface ofthe duct to provide a configuration of large face area and short flowdepth, said first and second baffles permitting all of the fluid in saidduct to pass through the full face area of said heat exchanger meanswhen in position along the surface of said duct, means for moving saidfirst and second baffles inwardly from the duct surface to reverse theflow of air through adjacent sections and pass all the fluid flowserially through each section to provide a configuration of small facearea and long flow depth, inlet and discharge passages for a coolantutilized in said heat exchanger means, and valve means in said inlet anddischarge passages for regulating the flow of coolant to said sectionsto maintain cross counter flow of the coolant for both configurations,said heat exchanger means comprising three sections, said valve means insaid inlet passage distributing the coolant equally to said threesections on the downstream side and said valve means in said dischargepassage discharging the coolant equally from the upstream side of. theheat exchanger sections when both said first and second battles are inposition along the surface of said duct to provide a large face area anda small flow depth, said valve means in said inlet and discharge passageintroducing fluid to the first section on the downstream, then to thesecond section on the upstream and finally to the third section on thedownstream side to maintain cross counter flow when the first and secondbaffles are in their inward positions to provide a small face area and along flow 7 depth, each of said valve means comprising avalve plugslidable in a valve housing connected with passages leading to the heatexchanger sections, each of said valve plugs containing two separatesets of valve passages, the first set of valve passages in each plugbeing operative simul-. taneously for one configuration of ,said heatexchanger means and the second set being operative simultaneously forthe other configuration of said heat exchanger means.

2. A heat transfer device as defined in claim '1 having actuator meansfor moving the first andsecond bafiles and having valve actuator meansfor moving said valve plugs upon change in configuration of said bafles.

3. A heat transfer device as defined in claim 2 wherein said secondbaffle in its inwardly extending position extends between the :uppersurface and .said second and third sections.

the junction between References Cited in the file ofthis patent UNITEDSTATES PATENTS 1,634,903 l Hodgkinson "July 5,1927

I 1,922,220 Sprag ue Aug. 15, 1933 2,213,324 Niemitz Sept. 3, 19402,487,484 Sirripelaar ..Nov. 8, 1949 2,930,593 Blum Mar. 29, 1960FOREIGN PATENT S 7 1,067,337 France Jan. 27, '1954

1. A HEAT TRANSFER DEVICE HAVING A CONFIGURATION VARIABLE WITH OPERATINGCONDITIONS COMPRISING HEAT EXCHANGER MEANS LOCATED TRANSVERSELY WITHIN ADUCT THROUGH WHICH FLOWS A FLUID TO BE COOLED, SAID HEAT EXCHANGER MEANSCOMPRISING A PLURALITY OF HEAT EXCHANGER SECTIONS LOCATED SIDE BY SAIDIN A PLANE TRANSVERSELY ACROSS SAID DUCT, A FIRST MOVABLE BAFFLE LOCATEDWITHIN SAID DUCT UPSTREAM OF SAID HEAT EXCHANGER MEANS AND LOCATED ALONGTHE SURFACE OF THE DUCT TO PROVIDE A CONFIGURATION OF LARGE FACE AREAAND SHORT FLOW DEPTH, A SECOND MOVABLE BAFFLE LOCATED WITHIN SAID DUCTDOWNSTREAM OF SAID HEAT EXCHANGER MEANS AND LOCATED ALONG THE SURFACE OFTHE DUCT TO PROVIDE A CONFIGURATION OF LARGE FACE AREA AND SHORT FLOWDEPTH, SAID FIRST AND SECOND BAFFLES PERMITTING ALL OF THE FLUID IN SAIDDUCT TO PASS THROUGH THE FULL FACE AREA OF SAID HEAT EXCHANGER MEANSWHEN IN POSITION ALONG THE SURFACE OF SAID DUCT, MEANS FOR MOVING SAIDFIRST AND SECOND BAFFLES INWARDLY FROM THE DUCT SURFACE TO REVERSE THEFLOW OF AIR THROUGH ADJACENT SECTIONS AND PASS ALL THE FLUID FLOWSERIALLY THROUGH EACH SECTION TO PROVIDE A CONFIGURATION OF SMALL FACEAREA AND LONG FLOW DEPTH, INLET AND DISCHARGE PASSAGES FOR A COOLANTUTILIZED IN SAID HEAT EXCHANGER MEANS, AND VALVE MEANS IN SAID INLET ANDDISCHARGE PASSAGES FOR REGULATING THE FLOW OF COOLANT TO SAID SECTIONSTO MAINTAIN CROSS COUNTER FLOW OF THE COOLANT FOR BOTH CONFIGURATIONS,SAID HEAT EXCHANGER MEANS COMPRISING THREE SECTIONS, SAID VALVE MEANS INSAID INLET PASSAGE DISTRIBUTING THE COOLANT EQUALLY TO SAID THREESECTIONS ON THE DOWNSTREAM SIDE AND SAID VALVE MEANS IN SAID DISCHARGEPASSAGE DISCHARGING THE COOLANT EQUALLY FROM THE UPSTREAM SIDE OF THEHEAT EXCHANGER SECTIONS WHEN BOTH SAID FIRST AND SECOND BAFFLES ARE INPOSITION ALONG THE SURFACE OF SAID DUCT TO PROVIDE A LARGE FACE AREA ANDA SMALL FLOW DEPTH, SAID VALVE MEANS IN SAID INLET AND DISCHARGE PASSAGEINTRODUCING FLUID TO THE FIRST SECTION ON THE DOWNSTREAM, THEN TO THESECOND SECTION ON THE UPSTREAM AND FINALLY TO THE THIRD SECTION ON THEDOWNSTREAM SIDE TO MAINTAIN CROSS COUNTER FLOW WHEN THE FIRST AND SECONDBAFFLES ARE IN THEIR INWARD POSITIONS TO PROVIDE A SMALL FACE AREA AND ALONG FLOW DEPTH, EACH OF SAID VALVE MEANS COMPRISING A VALVE PLUGSLIDABLE IN A VALVE HOUSING CONNECTED WITH PASSAGE LEADING TO THE HEATEXCHANGER SECTIONS, EACH OF SAID VALVE PLUGS CONTAINING TWO SEPARATESETS OF VALVE PASSAGES, THE FIRST SET OF VALVE PASSAGES IN EACH PLUGBEING OPERATIVE SIMULTANEOUSLY FOR ONE CONFIGURATION OF SAID HEATEXCHANGER MEANS AND THE SECOND SET BEING OPERATIVE SIMULTANEOUSLY FORTHE OTHER CONFIGURATION OF SAID HEAT EXCHANGER MEANS.